Add cljs-repl support

[lsnape]

Lately I've been thinking about how to improve the cljs development and testing workflow. Running cljs tests when the project files change is reasonably straightforward to set up, and is useful for catching regressions in existing tests. But for writing new unit tests we're restricted to the browser we're developing in. This can be a pain because state from the running app leaks in (js/Document etc.).

What I'd love to be able to do is connect a cljs-repl to a separate test environment, so I can write my tests interactively and independently of the browser running my app. I think this is achievable if we could modify the runner to connect to a reload cljs websocket before it runs the tests, and then perhaps optionally rerun the tests on reload.

How does this idea sound? IMO It would be great if doo had this support. I'll happily have a stab at implementing it.

Cheers,

Luke